The ruling effectively means that, barring a successful appeal, the controversial measure that focused attention nationwide on the problem of illegal immigration will never be fully implemented.

"Proposition 187, as drafted, is not constitutional on its face," Judge Mariana R. Pfaelzer declared in a 32-page opinion.

Although observers had long anticipated the finding, much of the judge's decision turned on a relatively new law--last year's sweeping congressional reform of the federal welfare system, known as the Personal Responsibility and Work Opportunity Reconciliation Act of 1996. Proposition 187 served as a catalyst for many of that law's far-reaching restrictions on benefits for immigrants, those here legally as well as illegal residents.

The 1996 welfare statute, the judge ruled, "serves to reinforce" her prior finding that Proposition 187 is a "scheme" designed to regulate immigration, an exclusively federal domain. State officials seeking to restrict immigrant access to benefits must live by the guidelines outlined in the new federal law, she ruled.

"California is powerless to enact its own legislative scheme to regulate immigration," Pfaelzer said. "It is likewise powerless to enact its own legislative scheme to regulate alien access to public benefits."

The judge cited as unlawful the initiative's major sections--those barring illegal immigrants from receiving publicly funded education, social services and health care--along with provisions mandating that local law enforcement authorities, school administrators, social workers and health care aides turn in suspected illegal immigrants.

However, the judge did let stand two less controversial sections that establish state criminal penalties for the manufacture and use of false documents to conceal immigration status.

The judge requested that attorneys submit additional motions by Nov. 28, but lawyers on both sides of the issue said the decision clearly signals that she will soon issue a permanent injunction to replace the existing temporary ban. The final order could come by the end of the year, attorneys said.

At that point, the battle surrounding the disputed measure will move to the U.S. 9th Circuit Court of Appeals, where Gov. Pete Wilson and other Proposition 187 supporters are expected to seek a rebuke of Pfaelzer's ruling. Most expect the matter to end up in the Supreme Court, possibly as soon as next fall.

"This is the tombstone for Proposition 187," said Mark Rosenbaum of the American Civil Liberties Union of Southern California, co-counsel in the case against the initiative.

Although they condemned the judge's ruling, proponents of Proposition 187 were relieved that the matter finally seemed to be leaving the courtroom of Pfaelzer, whom Proposition 187 supporters have excoriated as a biased jurist who sat on the case for more than three years in a delaying tactic. Wilson even took the unusual step of filing papers with the U.S. Court of Appeals this week demanding that the judge take action--a move that anti-187 activists called a publicity stunt.

"We're free at last!" exclaimed Ron Prince, the Orange County accountant who rose to national prominence as a co-author of Proposition 187 and an advocate of tighter controls on illegal immigration.

But he, Wilson, state Atty. Gen. Dan Lungren and other supporters of the ballot initiative were highly critical of Pfaelzer's decision to invoke last year's federal welfare overhaul as a major rationale for throwing out Proposition 187. California authorities had argued the exact opposite: that Proposition 187 was consistent with the federal legislation.

The passage of the welfare law last year prompted some in the governor's office to predict that it opened the way for the implementation of much of Proposition 187.

"I find that Judge Pfaelzer's interpretation of Congress' intent when drafting the federal welfare law defies all logic," said Lungren, a former ranking House Republican on immigration matters.

Added Wilson: "Her analysis of Proposition 187 is as flawed and error-prone as the 1962 New York Mets. We look forward to this measure going to a higher court that has a better understanding of the law." But those fighting the ballot measure said the judge's ruling was on target and would probably resist arguments on appeal.

"The judge has vindicated the principle that we can't have 50 immigration policies, we can only have one," said Thomas Saenz, an attorney with the Mexican American Legal Defense and Educational Fund.

Other opponents delighted in the irony of Pfaelzer using the federal welfare overhaul--a law championed by Wilson and Republican leaders--as a legal battering ram against Proposition 187, which also had strong GOP backing.